/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.eelpo.common.download;

import java.io.Serializable;

/**
 * Enumeration of IO case sensitivity.
 * <p>
 * Different filing systems have different rules for case-sensitivity. Windows
 * is case-insensitive, Unix is case-sensitive.
 * <p>
 * This class captures that difference, providing an enumeration to control how
 * filename comparisons should be performed. It also provides methods that use
 * the enumeration to perform comparisons.
 * <p>
 * Wherever possible, you should use the <code>check</code> methods in this
 * class to compare filenames.
 * 
 * @author Stephen Colebourne
 * @version $Id: IOCase.java 1003647 2010-10-01 20:53:59Z niallp $
 * @since Commons IO 1.3
 */
public final class IOCase implements Serializable {

	/**
	 * The constant for case sensitive regardless of operating system.
	 */
	public static final IOCase SENSITIVE = new IOCase("Sensitive", true);

	/**
	 * The constant for case insensitive regardless of operating system.
	 */
	public static final IOCase INSENSITIVE = new IOCase("Insensitive", false);

	/**
	 * The constant for case sensitivity determined by the current operating
	 * system. Windows is case-insensitive when comparing filenames, Unix is
	 * case-sensitive.
	 * <p>
	 * <strong>Note:</strong> This only caters for Windows and Unix. Other
	 * operating systems (e.g. OSX and OpenVMS) are treated as case sensitive if
	 * they use the Unix file separator and case-insensitive if they use the
	 * Windows file separator (see {@link java.io.File#separatorChar}).
	 * <p>
	 * If you derialize this constant of Windows, and deserialize on Unix, or
	 * vice versa, then the value of the case-sensitivity flag will change.
	 */
	public static final IOCase SYSTEM = new IOCase("System", !FilenameUtils.isSystemWindows());

	/** Serialization version. */
	private static final long serialVersionUID = -6343169151696340687L;

	/** The enumeration name. */
	private final String name;

	/** The sensitivity flag. */
	private final transient boolean sensitive;

	// -----------------------------------------------------------------------
	/**
	 * Factory method to create an IOCase from a name.
	 * 
	 * @param name
	 *            the name to find
	 * @return the IOCase object
	 * @throws IllegalArgumentException
	 *             if the name is invalid
	 */
	public static IOCase forName(String name) {
		if (IOCase.SENSITIVE.name.equals(name)) {
			return IOCase.SENSITIVE;
		}
		if (IOCase.INSENSITIVE.name.equals(name)) {
			return IOCase.INSENSITIVE;
		}
		if (IOCase.SYSTEM.name.equals(name)) {
			return IOCase.SYSTEM;
		}
		throw new IllegalArgumentException("Invalid IOCase name: " + name);
	}

	// -----------------------------------------------------------------------
	/**
	 * Private constructor.
	 * 
	 * @param name
	 *            the name
	 * @param sensitive
	 *            the sensitivity
	 */
	private IOCase(String name, boolean sensitive) {
		this.name = name;
		this.sensitive = sensitive;
	}

	/**
	 * Replaces the enumeration from the stream with a real one. This ensures
	 * that the correct flag is set for SYSTEM.
	 * 
	 * @return the resolved object
	 */
	private Object readResolve() {
		return forName(name);
	}

	// -----------------------------------------------------------------------
	/**
	 * Gets the name of the constant.
	 * 
	 * @return the name of the constant
	 */
	public String getName() {
		return name;
	}

	/**
	 * Does the object represent case sensitive comparison.
	 * 
	 * @return true if case sensitive
	 */
	public boolean isCaseSensitive() {
		return sensitive;
	}

	// -----------------------------------------------------------------------
	/**
	 * Compares two strings using the case-sensitivity rule.
	 * <p>
	 * This method mimics {@link String#compareTo} but takes case-sensitivity
	 * into account.
	 * 
	 * @param str1
	 *            the first string to compare, not null
	 * @param str2
	 *            the second string to compare, not null
	 * @return true if equal using the case rules
	 * @throws NullPointerException
	 *             if either string is null
	 */
	public int checkCompareTo(String str1, String str2) {
		if (str1 == null || str2 == null) {
			throw new NullPointerException("The strings must not be null");
		}
		return sensitive ? str1.compareTo(str2) : str1.compareToIgnoreCase(str2);
	}

	/**
	 * Compares two strings using the case-sensitivity rule.
	 * <p>
	 * This method mimics {@link String#equals} but takes case-sensitivity into
	 * account.
	 * 
	 * @param str1
	 *            the first string to compare, not null
	 * @param str2
	 *            the second string to compare, not null
	 * @return true if equal using the case rules
	 * @throws NullPointerException
	 *             if either string is null
	 */
	public boolean checkEquals(String str1, String str2) {
		if (str1 == null || str2 == null) {
			throw new NullPointerException("The strings must not be null");
		}
		return sensitive ? str1.equals(str2) : str1.equalsIgnoreCase(str2);
	}

	/**
	 * Checks if one string starts with another using the case-sensitivity rule.
	 * <p>
	 * This method mimics {@link String#startsWith(String)} but takes
	 * case-sensitivity into account.
	 * 
	 * @param str
	 *            the string to check, not null
	 * @param start
	 *            the start to compare against, not null
	 * @return true if equal using the case rules
	 * @throws NullPointerException
	 *             if either string is null
	 */
	public boolean checkStartsWith(String str, String start) {
		return str.regionMatches(!sensitive, 0, start, 0, start.length());
	}

	/**
	 * Checks if one string ends with another using the case-sensitivity rule.
	 * <p>
	 * This method mimics {@link String#endsWith} but takes case-sensitivity
	 * into account.
	 * 
	 * @param str
	 *            the string to check, not null
	 * @param end
	 *            the end to compare against, not null
	 * @return true if equal using the case rules
	 * @throws NullPointerException
	 *             if either string is null
	 */
	public boolean checkEndsWith(String str, String end) {
		int endLen = end.length();
		return str.regionMatches(!sensitive, str.length() - endLen, end, 0, endLen);
	}

	/**
	 * Checks if one string contains another starting at a specific index using
	 * the case-sensitivity rule.
	 * <p>
	 * This method mimics parts of {@link String#indexOf(String, int)} but takes
	 * case-sensitivity into account.
	 * 
	 * @param str
	 *            the string to check, not null
	 * @param strStartIndex
	 *            the index to start at in str
	 * @param search
	 *            the start to search for, not null
	 * @return the first index of the search String, -1 if no match or
	 *         <code>null</code> string input
	 * @throws NullPointerException
	 *             if either string is null
	 * @since Commons IO 2.0
	 */
	public int checkIndexOf(String str, int strStartIndex, String search) {
		int endIndex = str.length() - search.length();
		if (endIndex >= strStartIndex) {
			for (int i = strStartIndex; i <= endIndex; i++) {
				if (checkRegionMatches(str, i, search)) {
					return i;
				}
			}
		}
		return -1;
	}

	/**
	 * Checks if one string contains another at a specific index using the
	 * case-sensitivity rule.
	 * <p>
	 * This method mimics parts of
	 * {@link String#regionMatches(boolean, int, String, int, int)} but takes
	 * case-sensitivity into account.
	 * 
	 * @param str
	 *            the string to check, not null
	 * @param strStartIndex
	 *            the index to start at in str
	 * @param search
	 *            the start to search for, not null
	 * @return true if equal using the case rules
	 * @throws NullPointerException
	 *             if either string is null
	 */
	public boolean checkRegionMatches(String str, int strStartIndex, String search) {
		return str.regionMatches(!sensitive, strStartIndex, search, 0, search.length());
	}

	// -----------------------------------------------------------------------
	/**
	 * Gets a string describing the sensitivity.
	 * 
	 * @return a string describing the sensitivity
	 */
	@Override
	public String toString() {
		return name;
	}

}
